Specific Heat of Diatomic gases (rigid)
- A rigid diatomic gas means they will have translational as well as rotational degree of freedom but not vibrational.
- They are rigid oscillator.
- A rigid diatomic molecule will have 3 translational degrees of freedom and 2 rotational degrees of freedom. Total 5 degrees of freedom.
- By law of equipartition of energy, each degree of freedom will contribute (1/2) kB
- Therefore 5 degree of freedom will contribute (5/2) kB
- Therefore the total internal energy of 1 mole of gas, U=(5/2) kBTxNA=(5/2)RT
- Specific heat capacity at constant volume(CV) =dU/dT=(5/2)R
- Specific heat capacity at constant pressure of a rigid diatomic is given as CP=(7/2)R
- Ratio of specific heats γ=CP/CV=(7/5)